Photographic element containing an oil-soluble vinylene brightening agent

ABSTRACT

HYDROPHILIC COLLOIDS HAVING INTIMATELY DISPERSED THEREIN AN ESSENTIALLY HYDROPHOBIC SOLID SOLUTION OF AN OILSOLUBLE VINYLENE BRIGHTENING AGENT IN AN ESSENTIALLY HYDROPHOBIC ORGANIC SOLVENT THAT IS RIGID (AN ORGANIC GLASS) AT ROOM TEMPERATURE, I.E., HAS A GLASS TRANSITION TEMPERATURE (TG) THAT IS ABOVE ABOUT 25*C. ARE ADVANTAGEOUSLY USED IN PHOTOGRAPHIC ELEMENTS AND IN IMAGE-RECEIVING ELEMENTS FOR IMAGE DIFFUSION TRANSFER BECAUSE THE LIGHT-STABILITY OF THE STIBENE BRIGHTENING AGENTS IN THESE DISPERSIONS IS INCREASED SUBSTANTIALLY OVER THE LIGHT-STABILITY OF THE SAME BRIGHTENING AGENTS IN DISPERSIONS OUTSIDE THE IMMEDIATE INVENTION.

United States Patent 3,788,854 J PHOTOGRAPHIC ELEMENT CONTAINING AN OIL-SOLUBLE VINYLENE BRIGHTENING AGENT Robert J. Tuite, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y. No Drawing. Continuation of abandoned application Ser. No. 847,404, Aug. 4, 1969. This application Jan. 31, 1972, Ser. No. 222,304

Int. Cl. G03c 1/92 US. Cl. 96-82 15 Claims ABSTRACT OF THE DISCLOSURE This is a continuation of application Ser. No. 847,404, tiled Aug. 4, 1969, now abandoned.

This invention relates to brightening compositions having greatly improved stability, a method for improving the stability of brighteners, and photographic materials containing brightener compositions having improved stability.

The highlight areas of photographic color prints and other products, such as, fibrous or plastic articles are often made to look whiter by incorporating optical brightening agents. These brightening agents, fluoresce under radiation with ultraviolet light, emitting visible light, usually bluish in hue thus enhancing the whiteness of the object. Such products also frequently contain ultraviolet sensitive ingredients such as dyes, organic polymers, etc., which require protection from irradiation in the ultraviolet region, especially from 360400 m Brighteners are inherently ultraviolet absorbers and depend on this characteristic for the energy required to fiuoresce in the visible region of the spectrum. Most of the known brightening agents are decomposed by prolonged exposure to ultraviolet radiation, and thus lose their ability to fluoresce and serve as brightening agents. Brighteners containing substituted vinylene groups, e.g., stilbenes, styrenes and vinylenes are well known and are efiicient brighteners which absorb and fluoresce in desirable regions of the spectrum. These brightening agents, however, do not have the desired stability to prolonged exposure to radiation.

It is known to use high boiling solvents, such as, benzyl alcohol, diethyl esters of phthalic acid, etc., which are wholly, or partly replaced by resins such as polystyrene, polyvinyl acetate, and an ester of polyacrylic acid, to dissolve brighteners such as stilbene for dispersing in aqueous gelatin solution before coating photographic elements. Such methods are described in Ger-man Pat. 1,150,- 274. However, brightening compositions made by these methods either have low fluorescence or do not have the desired stability to prolonged exposure to light.

It is therefore an object of my invention to provide novel vinylene brightener compositions which have substantially improved stability to prolonged exposure to light.

It is another object of my invention to provide a method for making my novel vinylene brightener compo- "ice sitions which have greatly improved stability to prolonged exposure to light.

Another object of my invention is to provide novel, photographic elements which contain my novel vinylene brightener compositions.

These and still other objects will become apparent from a consideration of the following specification and claims.

These and other objects are accomplished according to my invention by the preparation and use of my novel vinylene brightener compositions in photographic elements andin image receiving elements. My brightener compositions comprise hydrophilic colloids having intimately dispersed therein an essentially hydrophobic solid solution of an oil-soluble vinylene brightening agent in an essentially hydrophobic organic solvent that is rigid (an organic glass) at room temperature, i.e., has a glass transition temperature (Tg) above about 25 C. My brightening compositions are valuable because they have unexpectedly good stability to prolonged exposure to ultra-violet radiation. My brightening compositions are advantageously made by dissolving any oil-soluble vinylene brightening agent in a rigid organic permanent solvent and a temporary liquid solvent and then dispersing the resulting hydrophobic liquid solution into an aqueous hydrophilic colloid solution. The temporary solvent is then removed by evaporation or washing, leaving the dispersion of particles of the solid solution of my vinylene brightening agent in the permanent, rigid, organic solvent so the particles have average diameters that are very small, usually less than .4 micron and preferably less than .1 micron. It is important that my brightener solution particles be dispersed in an aqueous hydrophilic colloid binder.

Included among the oil-soluble vinylene brightening agents used to advantage according to my invention are those having the formula:

wherein T represents a bivalent vinylene group, e.g., a vinylene group, a styrene group and a stilbene group; G and G each represent a members such as C or N; X and X each represent a member such as O, S and NR, N and CR; such that when G and G each represent C, then X and X each represent a member such as 0, S and NR, and such that when G and G each represent N, then X and X each represent a member such as N and CR; R represents a member, such as, hydrogen, an alkyl group having from 1 to 22 carbon atoms (e.g., methyl, ethyl, benzyl, phenethyl, decyl, dodecyl, docosyl, etc.) and an aryl group, preferably a phenyl group (e.g., phenyl, tolyl, chlorophenyl, ethylphenyl, bromophenyl, etc.); M and M each represent the nonmetallic atoms required to complete a heterocyclic ring, such as, an oxazole group, a benzoxazole group, a naphthoxazole group, a thiazole group, a benzothiazole group, a naphthathiazole group, an imidazole group, a benzimidazole group, a naphthimidazole group, a triazole group, a benzotriazole group and a naphthotriazole group; n is an integer of from 1 to 2; G represents a member, such as, hydrogen, an alkyl group and an aryl group.

My oil-soluble vinylene brightening agents include heterocyclic substituted vinylene groups (e.g., vinylene, a styrene group, a stilbene group, etc.). The stilbenes have attached to at least one of their 4 and 4', 4 and 2', 2 and 4 or 4 and 3' positions, a heterocyclic group such as an oxazole group, a thiazole group and a triazole group etc.

My oil-soluble brightening agents include the formula:

wherein G, G, G X, X and n are defined previously; m and p each represent integers of from 1 to 2; such that when p is l, n is 2; R, R R R R R R R and R each represents any monovalent substituent which does not destroy the desirable fluorescent properties of the stil- 'bene brighteners including such members as hydrogen, a halogen atom (e.g., chlorine, bromine, fluorine and iodine atoms), hydroxyl, an acyl group (e.g., acetyl, butyryl, dodecoyl, benzoyl, etc.), an acyloxy group (e.g., acetoxy, butyryloxy, dodecoyloxy, benzoyloxy, etc.), an amino group (e.g., amino, ethylamino, diethylamino, lhydroxyethylamino, methoxyethylamino, benzylamino, cyclohexylamino, phenylamino, octadecylamino, docosylamino, etc.), a sulfonyl group, such as an alkylsulfonyl group (e.g., methyl sulfonyl, benzylsulfonyl, dodecylsulfonyl, docosylsulfonyl, etc.), an arylsulfonyl group, such as, a phenylsulfonyl group (e.g., phenylsulfonyl, tolylsulfonyl, ethoxyphenylsulfonyl, chlorophenylsulfonyl, etc.), a naphthylsulfonyl (e.g., a-naphthylsulfonyl, B-naphthylsulfonyl, etc.), a sulfamyl group (e.g., sulfamyl, N-methylsulfamyl, N,N-dimethylsulfamyl, N-docosylsulfamyl, N benzylsulfamyl N-phenylsulfamyl, N-tolylsulfamyl, N- chlorophenylsulfamyl, etc.), cyano, thiocyano', thiol, a carbamyl group (e.g., carbamyl, N-methylcarbamyl, N,N- dimethylcarbamyl, N-benzylcarbamyl, N-docosylcarbamyl, N-tolylcarbamyl, N-(chlorophenyl)carbamyl, N-(anaphthyl)carbamyl, etc.), a carbamyloxy group (e.g., carbamoyloxy, methylcarbamoyloxy, butylcarbamoyloxy, phenylcarbamoyloxy, u-naphthylcarbamoyloxy, etc.), an alkyl group having from 1 to 22 carbon atoms, e.g., methyl, benzyl, ethyl, phenethyl, ethylphenethyl, isopropyl, butyl, t-butyl, 2,2-difiuoroethyl, 4,4-difluoro-n-butyl, 2,2,2-

those having group,a

octyl, decyl, octadecyl, docosyl, etc.), an alkoxy group having from 1 to 22 carbon atoms (e.g., methoxy, ethoxy, phenethoxy, butoxy, decyloxy, pcntadecyloxy, octadecyloxy, docosyloxy, etc.), an aryl group, such as, a phenyl group (e.g., phenyl, tolyl, ethylphenyl, chlorophenyl, bromophenyl, methoxyphenyl, ethoxyphenyl, etc.), a naphthyl group (e.g., a-naphthyl, fi-naphthyl, etc.), an aryloxy group, such as, a phenoxy group (e.g., phenoxy, tolyloxy, chlorophenoxy, hydrophenoxy, etc.), a naphthyloxy group (e.g., a-naphthoxy, p-naphthoxy, etc.), a furyl group, a

group; Q and Q each represent a hydrogen atom, an alkyl group (e.g., methyLethyl, butyl, decyl, cyclobutyl, cyclohexyl, methoxyethyl, chloroethyl, etc.), an aryl group, preferably a phenyl group (e.g., phenyl, tolyl, ethylphenyl, methoxyphenyl, ethoxyphenyl, chlorophenyl, bromophenyl, etc.); Q represents an alkyl group or an aryl group, each as described for Q; L represents an acyl group (e.g., acetyl, butyryl, dodecoyl, benzoyl, etc.), a ureido group; Q and Q are as defined previously; R and R can be any monovalent substituent that does not destroy the desirable fluorescent properties of the stilbene compound, including hydrogen, alkyl having from 1 to 15 carbon atoms (e.g., methyl, ethyl, butyl, 2-ethylhexyl, pentadecyl, etc.), an aryl group, preferably a phenyl group (e.g., phenyl, tolyl, methoxyphenyl, chlorophenyl, bromophenyl, etc); Z and Z each represent a member, such as, hydrogen, an alkyl group having from 1 to 22 carbon atoms as defined previously for R an aryl group including a phenyl group as defined previously for R and a naphthyl group as previously defined for R and taken together Z and Z represent the nonmetallic atoms required to complete rings represented by the formulas I I R1 R14 Rn u 1o V R11 Ru R i R 11 B1 B1: or I such that the unsubstituted carbons in these rings are also in the heterocyclic rings to which they are used; R R R R R and R each represent a member, such as, hydrogen, a halogen, hydroxyl, an acyl group, an acyloxy group, an amino group, a substituted sul-fonyl group, a sulfamyl group, cyano, thiocyano, thiol, a carbamyl group, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, furyl, and thienyl, each as de fined previously for R through R and Z and 2, each represent a member, such as, hydrogen, an alkyl group having from 1 to 22 carbon atoms as definedpreviously for R an aryl group including a phenyl group as defined previously for R and a naph-thyl group as previously defined for R and taken together Z and Z represent the (74) 4,4'-bis(6-thiomethylbenzoxazol-Z-yl) 2,2-

dimethylstilbene (75 4,4'-bis( 6-cyanobenzoxazol-2-yl) -2,2'-dimethy1- stilbene (76) 4,4-bis (6-acetamidobenzoxazol-2-yl) -2,2'-dimethy1- stilbene (77) 4,4'-bis(5-chlorobenzoxazol-2-yl)-2-chlorostilbene (78) 4,4-bis(S-methoxybenzoxazol-Z-yl)-2-methylstilbene (79) 4,4-bis (S-bromobenzoxazol-Z-yl) -2-methylstilbene (80) 4,4'-bis(5-thiomethylbenzoxazol-Z-yl)-2-methylstilbene (81 4,4'-bis( -dimethylsulfamylbenzoxazol-Z-yl -2- methylstilbene (82) 4,4'-bis(S-trifluoromethylbenzoxazol-Z-yl)-2- methylstilbene 83 4,4'-bis(S-iodobenzoxazol-Z-yl)-2-methy1stilbene (84) 4,4'-bis(S-methoxybenzoxazol-Z-yl)-2-cyanostilbene (85) 4,4-bis(S-methylbenzoxazol-Z-yl)-2-cyanostilbene ('86) 4,4-bis(5-p-methoxyphenylbenzoxazol-Z-yl)-2- cyanostilbene (87) 4,4'-bis(S-trifluoromethylbenzoxazol-Z-yl)-2- cyanostilbene (88 4,4'-bis 5-carbomethoxybenzoxazol-Z-yl) -2-cyanostilbene (89) 4,4'-bis(5-acetamidobenzoxazol-2-yl)-2-cyanostilbene (90) 4,4-bis(S-cyanobenzoxazol-Z-yl)-2-cyanostilbene (91) 4,4'-bis(G-ethoxybenzoxazol-Z-yl)-a-cyanostilbene (92) 4,4-bis(-6-phenoxybenzoxazol-2-yl)-a-cyanostilbene (93 4,4'-bis ('6- [p-methoxyphenoxy] benzoxazol-Z-yl) a-cyanostilbene (94) 4,4'-bis(6-carbomethoxybenzoxazol-Z-yl)ant-cyanostilbene (95) 4,4'-bis(6-methoxybenzoxazol-2-yl)-a-cyanostilbene (96) 4,4'-bis(S-ethoxybenzoxazol-Z-yl)-a-cyano-2- methyl-3'-chlorostilbene (97) 4,4'-bis(6-methoxybenzoxazol-2-yl)-a-cyano-2- methyl-3'-chlorostilbene.

Essentially hydrophobic rigid organic solvents having a glass transition temperature, i.e., Tg, above about 25 C. used to advantage according to my invention are preferably photographically inert, i.e., do not change the sensitivity or developability of silver halide emuslions; they are compatible with the photographic processing solutions, are preferably colorless, transparent or translucent and have a refractive index that is in the same general range as the refractive index of the hydrophilic of allracrylatef has from 1' to about 5 carbons), polycolloid that it is to be dispersed in. My rigid solvents are nondiffusible in the hydrophilic colloid layers containing them. My rigid solvents include polymers (i.e., homopolymers, copolymers, terpolymers, etc.), mixtures of polymers, etc. such that the solvent has a Tg above about 25 C. (ambient room temperature) and preferably above 40 C. When a physical mixture of compounds (as opposed to, for example, a copolymer) is used as my solvent, it is not the Tg of the individual components that is important, but the Tg of the composite mixture.

The glass transition temperature range is the range of temperatures over which the specific heat and thermal coefiicient of expansion of an amorphous material undergoes discontinuities and is such that below this temperature range the material is glass-like in character and that above this temperature range, the material is fluidlike. The glass transition temperature, Tg, is the temperature coordinate of the upper asymptote of a graph of specific heat vs. temperature or thermal coefiicient vs. temperature and is the temperature at which a glass-like material becomes completely rubbery or fluid-like.

Rigid solvents used advantageously include polymers having recurring units of acrylonitrile, polymers having recurring units of at least one alkylalkacrylate (the alk 75 me r s having recurring units of f in which x is an integer of from 1 to about 12, etc., e.g.:

Solvent: Tg in C. Polyacrylonitrile 95 Poly(isobornyl methacrylate) 114 Poly(t-butyl methacrylate) 107 Poly(methyl methacrylate) 105 rv m h y a e) -.*f--,.;-i-..'- .1 Poly(ethyl methacrylate) 65 Poly(2-hydroxyethyl methacrylate) 55 Poly(n-propyl methacrylate) .L;... 35 Polycaprolactam (nylon 6) Polyhexamethylene adiparnide (nylon 6.6) 50 Polyhexamethylene sebacamide (nylon 6.10) 40 Copoly(butyl methacrylate acrylic acid) 85: 15 44 Copoly(butyl methacrylate methacrylic acid) 85:15 66 Copoly(methyl methacrylate butyl methacrylate) :45 Copoly(methyl methacrylate butyl methacrylate) 7 .,Copoly(methyl methacrylate butyl methacrylate) 95:5 100 Copoly(methyl methacrylate ethyl 'acrylate) 9515 VQ. I Copoly(methyl methacrylate ethyl acrylate) 50:50 29 Copoly(rnethyl methacrylate butyl acrylate) 90: 10 a 79 Copoly(methyl methacrylate butyl acrylate) 80:20 56 Copoly(methyl methacrylate butyl acrylate) I :30 g i 38 Copoly(methyl methacrylate methyl-"acrylatey 90:10 90 Copoly(methylmethacrylate methyl acrylate) 50:50 50 Copoly(methyl methacrylate 2-ethyl hexylacryl 1 ate) 90:10 4 7'1 Copoly(methyl methacrylate 2-ethyl hexylacrylate) :25 29 Terpoly(methyl methacrylate ethyl acylate butyl 1 methacrylate) 55:40:5 r 38 .Terpoly(methyl methacrylate ethyl acylate butyl methacrylate) 55:30:15 About 42 Terpoly (methyl methacrylate ethyl ,acrylate butyl methacrylate)v 55:15:30 52 Terpoly( methyl methacrylate ethyl acrylate butyl methacrylate) 55:5:40, 57 Terp0ly(methyl methacrylate ethyl acrylatebutyl I methacrylate) 90:5:5 90 Terpoly(methyl -methacrylate methyl acrylate butylacrylate) 50:30:20 30 Terpoly(methyl methacrylate methyl acrylate butylacrylate) 50:40:10 v 39 .Terpoly(methyl methacrylate methyl acrylate 1 butylacrylate) 50:45:05 [45 Terpo1y(methyl methacrylate methyl acrylate j butylacrylate) 70:15:15 .52' Terpoly(methyl methacrylate methyl acrylate ,I butylacrylate) 90:5 :5

Copoly(buty1 ethacrylate acrylic acid) 85:15. Copoly(butyl propacrylate acrylic acid) 85 :15. Copoly(butyl butacrylate acrylic acid) 85 :15.

The above and other rigid, organic, essentially hydro:

phobic solvents of my invention are used alone or in.

9 a Tg above about 25 C. The Tgs of mixtures can be estimated to a fair degree of accuracy by linear interpola tion between the Tgs of the components.

It is advantageous to use a temporary solvent in the preparation of my brightening agent dispersions. Any of the photographically inert, low boiling organic solvents for the brightening agents and rigid permanent solvent are used to advantage, including for example, nitromethe ane, nitroethane, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl formate, butyl formate, etc. Enough temporary solvent is used to make a liquid solution of the brightener and permanent solvent which is easily dispersed by conventional means into aqueous hydrophilic colloid. The temporary solvent, is removed from the dispersion by evaporation and/or bywashing, leaving a dispersion of a rigid solution of the brightening agent in the permanent solvent. Usually it is advantageous to prepare the dispersion so that the average diameter of the particles of rigid brightener solution in the permanent solvent is less than .4 micron. Very good dispersions have rigid brightener solution particles with an average diameter in the range from about .1 to about .2 micron and the preferred dispersions have rigid solution particles with an average diameter of less than 0.1 micron;

The ratio of brightening agent to permanent rigid solvent is usually in the range from about 1:1 to about 121000 parts by weight. A preferred ratio is in the range from about 1:10 to about 1:100. The optimum ratio will depend upon the particular materials being used and the results desired, and can be determined by methods well known in the art. i

It is important that my hydrophobic brightener solution particles be dispersed in a hydrophilic colloid so that the material can be coated from an aqueous composition, and so that there are no adhesion problems at the interface between the brightener layer and contiguous layers such as support, baryta layer, photographic emulsion layer, etc.

Any of the well-known hydrophilic colloids used in photographic elements are used to advantage, including gelatin, albumin, collodion, gum arabic, agar-agar, cellulose derivatives, such as, alkyl esters of carboxylated cellulose, hydroxy ethyl cellulose, carboxy methyl hydroxy ethyl cellulose, synthetic resins, such as the amphoteric copolymers described by Clavier et al. in U.S. Pat. 2,949,442, polyvinyl alcohol, polyvinyl pyrrolidone, and others well known in the art.

Any of the conventional photographic support materials are used advantageously for making my photographic elements, including photographic papersupport, paper coated with a reflection pigment, e.g., baryta (i.e. barium sulfate), titanium dioxide, zinc oxide, etc., paper or other fibrous material coated with a hydrophobic resin [e.g., poly(ethylene terephthalate), polyethylene, polypropylene, poly-(3-methylbutene-l), poly(octene-1), poly(decene-l), polyamides, polyacetals, polycarbonates, cellulose triacetate, cellulose acetate butyrate, ethyl cellulose, etc.] which are advantageously treated with corona discharge techniques just prior to coating the first gela tin layer over the resin as described in U.S. patents, such as 3,220,842, 2,864,755, 2,864,756, etc., glass, conventional photographic film supports, such as cellulose acetate, cellulose nitrate, etc., metal, etc. Baryta iscoated in the range from about .9 to 6.5 g./ft. preferably in range from 1.8 to 5.6 g./ft.

Any hydrophilic colloid silver halide emulsions'containing silver bromide, silver iodide, silver chloride, silver bromoiodide, silver chlorobromide, silver chlorobromoodide, etc., well known in black-and-white and color photography are used advantageously in my elements. The silver halide emulsion layers for my color elements advantageously contain color-forming couplers or are of the type that are color developed with color developer solutions containing the appropriate couplers.

My hydrophilic colloids having dispersed in them In rigid solution of stilbene brightening agent, are coated in photographic elements wherever an ultraviolet-absorbing brightener is needed, e.g., in over, or under a light-sensitive layer coated on any of the above supports, between two or morelight-sensitive layers on any of the above supports, in alayer containing a reflection pigment such as are described above, etc. A particularly advantageous utility for my brightener dispersions is in photographic print material, and in image-receiving elements for difiusion transfer.

The stilbene brightening agents dispersed according to my invention are substantially more stable to prolonged exposure to light than the same stilbene brightening agents dispersed in solvents outside my invention.

The following examples are included for a further understanding of my invention.

EXAMPLE 1 Solutions are made of 4,4-bis(5,7-di-t-amylbenzoxazol- 2-yl)stilbene in copoly(butyl methacrylate acrylic acid) :15 by weight, poly(t-'butyl methacrylate), and copoly- (butyl methacrylate methacrylic acid) 85 :15 by weight, each permanent solvent of my invention using enough of temporary solvent, i.e., ethyl acetate, to produce a liquid solution. Each of the three liquid solutions prepared are then dispersed in aqueous gelatin, the gelatin is chilled, noodled and the ethyl acetate removed by evaporation leaving a dispersion of minute rigid particles having an average diameter less than .4 micron and containing the 4,4-bis'(5,7 di t amylbenzoxazol 2 yl)stilbene dissolved in the indicated permanent solvent. The composition of each of the dispersions is such that when coated on a support there is 10 mg. of the brightener/ft 500 mg. of the permanent solvent/ft. and 500 mg. of gel atin/ftF. Coatings are made of each of the dispersions on a transparent support.

EXAMPLE 2 Example 1 is repeated using di-n-butylphthalate an oily solvent outside by invention, and copoly(butyl acrylate acrylic acid) 85 :15, a solvent outside my invention in place of the permanent solvents of my invention used in Example -1. The coatings are made so that the coating rates of brightener, permanent solvent and gelatin are the same as in Example 1. These coatings are used for controls in Example 3.

EXAMPLE 3 I The fresh coatings made in Examples 1 and 2 are compared for brightener fading caused by exposure to a SANS (Simulated Average North Skylight-500 ft. candle filtered Xenon Fadometer held at 70 F., 50% R-H- -1%) test. The brightener fading is monitored by plotting the density at 380 nm. vs. fading time and interpolating to obtain the half-life (T /2) of the 4,4 bis(5,7 di-t-amylbenzoxazol-2-yl)sti1bene in each of the coatings. The density values used in the plots are uncorrected for byproduct absorption, and corrected for stain present from solvent, gel and support. The results are summarized with the Tg values for the permanent solvents used.

acrylic acid) 85:15.

The results show that the brightener in my coating 3 has a half life that is about 267 times longer when dispersed as a solution in copoly(butyl methacrylate acrylic acid) 85:15 than when dispersed as a solution in di-nbutyl phthalate. It is not obvious from the half life of the brightener in control coating 2 that the same brightener in coating 3 of my invention would have a half life thatis almost 14 times'longer (than'in coating 2).

long as the half lifeof coating 6 using a permanent solvent having a Tg of -9l C. From these results with a 'thiophene' brighten'er outside my invention itis not obvious that permanent solvents having a Tgabove C. would give the very large improvement in thehalf life of the stilbene brighteners of my invention.

EXAMPLE 4 1 Example 1 is repeated using equivalentweights of 4-(a-naphthotriazol-2-yl)-4-octylstibene, v 4, (5,7 -di-t-amylbenzothiazol-2-yl) -4'- (4-octyloxazols- 2 -yl)stilbene, 1 p I 4,4-bis (5 -octylbenzoxazol-2-yl -a-methylstilbene, t u,,8-bis(5,7-dioctadecylbenzoxazol-2-yl)ethylene, 4,4-bis 6-methylsulfonylbenzoxazol-Z-yl) stilbene,. 4,4'-'bis(S-methoxybenzoxazol-2-yl)stilbene, 4,4'-bis 6-chlorobenzoxazol-2-yl) stilbene, a,fl-bis(6-docosylbenzoxazol-2-yl)ethylene, K. 4,4'-bis(5,7,-di-t-amylbenzoxazol-2-yl)-3,3f-dimethylstilbene, 4,4'-bis(benzoxazol-Z-yl)-2,2'-dioctadecylstilbene, 4,4'-bis(benzoxazol-2-yl)-2-phenylstilbene, 1 4,4'-bis 5,7-di-t-amylbenzoxazol-2-yl) -3,3'-dieth0xy stilbene, 4-(5,7-di-t-amylbenzothiazol-2yl)-4-phenylstilbene, 4,4-bis(S-chlorobenzothiazol-Z-yl(stilbene, 4,4'-bis 5,7-di-t-amylbenzimidazol-2-yl)stilbene, 4,4'-bis(6-octylbenzoimidazol-2-yl)stilbene, 4,;9-di(u-naphthoxazol-2-yl)styrene, 4,4-bis(fl, S-naphthoxazol-2-yl)stilbene, and 4,4'-bis(6-phenylbenzoxazol-2-yl)stilbene r in place of 4,4' di(5,7-di-t-amylbenzoxazol-2-yl)stilbene. The coatings made with these brightening agents in dispersions of my invention have very good stability to prolonged exposure to light.

EXAMPLE 5 Examples 1 and 4 are repeated using a paper support and also a paper support coated with a thin layer of polyethylene in place of the transparent support used' in Examples 1 and 4. The brightening agents in these coatings have very good stability to prolonged exposure to light.

EXAMPLE 6 Examples 1 and 4 are repeated using a baryta coated paper support in place of the transparent support used in the earlier examples. The brightening agents in these coatings have very good stability to prolonged exposureto light.

EXAMPLE 7 Examples 1 and 4 are repeated but dispersing amy brightener dispersion (after removal of the temporary solvent) into a baryta coating compositionand coating this on a paper suppor'tJT he brightening agents in these Y layer containing a dispersion of 4,4" bis(5,7-di-t-amylpoly(i sopropylmethacrylate), poly(2-hydroxyethyl methacrylate), poly(hexamethylene adipamide), polycaprolactam, copoly(butyl methacrylate methacrylic acid) '85 15, copoly (methyl methacrylate liiutyl methacrylate) 70:30, copoly (methylmethacrylate butyl' acrylate') 90: 10, copoly(methylmethacrylate methyl acrylate) :50, copoly(methylmethacrylate '2-e'thylhexylacrylate) 90: 10, terpoly(methyl methacrylate ethyl acrylate butylmethacryla'te) :15'i30, te rpoly(methyl methacrylate methyl acrylate butylacrylate) 70:15:15, polyacrylonitrile, and poly(ethylene glycol dimethacrylate) in place of the permanent" solvents used in Examples 1 and 4,. and coating the dispersions on pieces of a paper support instead .of a transparent support. The brightening agents in' these coatings of my invention have excellent stability to prolonged exposure to the SANS test.

EXAMPLE 9 The coatings made in Examples 1, 4, 5, 6, 7 and 8 are over coated with anordinary gleatin-silver chlorobromide emulsion. The dried coatings are given a light image exposure" andd'eveloped to a silver image with an aqueous alkaline solution containing hydroquinone and p-methylaminophenol followed by water washing, fixing in a con ventional alkali metal thiosulfate bath, washed and dried. The highlight'areas of the prints exhibit a high degree of brightening from the brighteners even after prolonged excoatings have very good stability' to prolonged: exposure to light.

EXAMPLE 8 poly(ethyl methacrylate), poly(isobornyl methacrylate), poly(methyl methacrylate),

posureto light. I

, EXAMPLE 10 A piece of photographic paper coated with a gelatin benzoxazol-Z-yDstil'bene dissolved in'copoly(butyl methacrylate acrylic acid) :15'anda dispersion of baryta is coated in succession (over said brightening layer) with (1) an ordinary blue-sensitive gelatino silver chlorobromide emulsion and a dispersion of a yellow dye-forming coupler'iof the type described in McCrossen et al. US. Pat. 2,875,057, (2)- a gelatin interlayer, (3) a gelatin layer containing an ordinary green-sensitized gelatinosilver chlorobromide emulsion, a dispersion of a magenta dye-forming coupler, such as, one of the couplers described in Loria et al. US. Pat. 2,600,788, (4) a gelatin layer, (5) a gelatin layer containing an ordinary redsensitized g'elatinosilver chlorobromide emulsion, a' dispersion of a cyan dyeforming coupler such as is described in Fierke U.S..Pat. 2,801,171, and (6) a gelatin protective layer.- The photographic element is exposed in an intensity scalesensitometer and then color processed as described in'Example 1, columns 5 and 6 of Van Campen US. Pat. 2,956,879 using 12' minutes development in the color developer. The processed color print has brightened highlights that even after prolonged ex'posureto light retain theirbrightness to a much higher degree than control color prints made'by the same way, excepting that the brightening agent is dispersed as a solution-indi-n butylphthalate. i I "f EXAMPLE/ 11 I Example 10 is-repeated, using. equivalent weights .of poly(tbuty1 methacrylate) and copoly(butyl methacrylate rnethacrylic acid) 85:15 (by weight) in place of copolybutyl methacrylate acrylic acid) 85: 15 used in Example 10. Results similar to those in Example 10 are obtained.

- EXAMPLE 12 Example 10 is repeated using equivalent weights of the brightening agents used in Example 4 in place of 4,4-

bis(5,7 di t-amylbenzoxazol 2-yl) stilbene used in Example 10. Resultssimilar to those in Example10 are obtained.

My brightening compositions are advantageously used in image-receiving elements that are used to receive diffusion transfer images during the diffusion transfer process; In these processes, a light-sensitive diffusion transfer element containing a light-image exposed silver halide emulsion is processed with the exposed emulsion layer in contact with the silver precipitating layer of an imagereceiving element in the presence of a silver halide developing agent, such as hydroquinone, l-phenyl-3-pyrazolidone, p-methylaminophenol, etc., a silver halide solvent or complexing agent, such as an alkali metal thiosulfate, ammonium thiosulfate, an alkali metal thiocyanate, ammonium thiocyanate, etc. In a particularly useful process, a thickening agent, such as carboxymethylcellulose, carboxyethylcellulose, etc. is used. During development, undeveloped silver halide forms a complex with the complexing agent which diffuses in an imagewise manner to the silver-precipitating layer on the image-receiving element where a silver image is precipitated from the silver halide complex. In an integral element, a silver halide emulsion coated over a silver precipitating layer is removed such as by washing, to disclose the transferred image. In a color diffusion transfer process, an imageexposed light-sensitive silver halide color diffusion transfer element is contacted with the receiving layer of an image-receiving element in the presence of a developer solution which causes the release of a dilfusible dye image that transfers to the mordanted receiving layer. The desired dye image remains in the receiving layer when the receiving element is separated from the developed diffusion transfer element. The diifusible dye image is formed from an incorporated non-diffusible coupler that couples with an imagewise pattern of oxidized primary aromatic amine color developing agent, produced by development of light-exposed silver halide. In another system, the dye image is formed from incorporated dye developing agents, such as hydroquinone derivatives that contain a chromophore as a substituent; the hydroquinone form of these compounds forms in the alkaline developer solution a diffusible dye while the dye developer that is oxidized to the quinone form (when it develops light-exposed silver halide to silver) is insoluble and does not diffuse to the image-receiving layer.

My brightening compositions are advantageously used in image-receiving elements- My image-receiving elements usually comprise a support as described previously that has been coated in succession with (1) a baryta layer containing my brightening composition, and (2) an imagereceiving layer for a silver image comprising any of the hydrophilic colloids such as have been described before, containing a dispersion of a silver precipitating agent or an image-receiving layer for a dye image comprising any of the hydrophilic colloids such as have been described before, containing a basic mordant for mordanting acid solubilized diffusible dyes. Usually it is advantageous to have a hydrophobic resin layer between the baryta layer and the image-receiving 1ayer.. Hydrophobic resins that are advantageously used include poly(ethylene terephthalate), polyethylene, polypropylene, poly(3-methylbutene-l), poly(octene-1), poly(decene-1), polyamides, polyacetate, polycarbonates, cellulose triacetate, cellulose acetate butyrate, ethyl cellulose, etc.; preferably the hydrophobic resin layer is treated with corona discharge techniques just prior to coating the first hydrophilic colloid layer over the resin as described in US. patents such as 3,220,842, 2,864,755, 2,864,756, etc. In one alternative structure, the baryta layer and brightening composition layers are coated separately between the support and image-receiving layer. In still another alternative structure, the image-receiving element comprises a support coated with a hydrophilic colloid layer containing both my brightening composition and a silver precipitating agent or mordant (for a dye transfer image).

Any suitable silver precipitant from the prior art is advantageously used in my receiving layer. As examples 14 v of suitable silver precipitating agents and of image-receiv ing elements containing such silver precipitating agents, reference may be made to US. Pat. Nos. 2,698,237, 2,698,238 and 2,698,245, issued to'Edwin H. Land on Dec. 28, 1954; US. Pat. No. 2,774,667, issued to Edwin H. Land and Meroe M. Morse on Dec. 18, 1956, US. Pat. No. 2,823,122, issued to Edwin H. Land on Feb. 11, 1958, US. Pat. No. 3,396,018, issued to Beavers et al., Aug. 6, 1968 and also US. Pat. 3,369,901, issued to Fogg et al., (Feb. 20, 1968. The noble metals, silver, gold, platinum, palladium, etc. in the colloidal form are particularly useful.

Noble metal nuclei are particularly active and useful when formed by reducing a noble metal salt using a borohydride or hydrophosphite in the presence of a colloid as described in Rasch, US. patent application Ser. No. 796,552, filed Feb. 4, 1969. The metal nuclei are prepared in the presence of a proteinaceous colloid such as gelatin and coated on the receiving element. The coating composition generally contains not only nuclei, but also reaction products which are obtained from reducing the metal salt.

The amount of colloid used in preparing the above active noble metal nuclei can be varied depending upon the particular colloid, reducing agent, ratio of proportions, etc. Typically, about 0.5% to about 20%, by weight, based on the total reaction mixture of colloid is used, preferably from about 1% to about 10%.

In a particularly useful embodiment, 30 to ,u.g./ft. of the active noble metal nuclei in 80 mg. of colloid (solids basis) is coated per square foot of support. The colloid binder is advantageously coated in a range of about 5 to about 500 mg./ft. Suitable concentrations on the receiving sheets of active noble metal nuclei as disclosed above can be about 1 to about 200 #g./ft. Other silver precipitants can be coated in a concentration of up to 5 mg./ft.

Any of the prior art mordants that have a charge opposite to the charge of the dye being transferred are used to advantage in my image-receiving elements for dye transfer images. Since most of the useful photographic imagetransfer dyes have acidic solubilizing groups, basic or cationic mordants are generally used. Typical mordants are organic quaternary phosphonium salts, organic ternary sulfonium salts and organic quaternary ammonium salts. Suitable mordants include polymers of amino guanidine derivatives of vinyl methyl ketone described in Minsk, US. Pat. 2,882,156. Other suitable mordants include the 2-vinyl pyridine polymer metho-p-toluene sulfonate, poly 4-vinylpyridine, thorium salts and similar compounds described in Sprague et al., US. Pat. 2,484,430.

A particularly useful class of mordanting compositions is disclosed in Bush, US. Pat. 3,271,147. Basic or cationic, nonpolymeric mordant compounds of Bush include quaternary ammonium and phosphonium, and ternary sulfonic composition in which there is linked to the N, P or S onium atom at least one hydrophobic ballast group, such as long-chain alkyl or substituted alkyl groups. The onium atom can be part of an open-chain or of a heterocyclic ring and there can be more than one onium ring in the molecule. When referring to the nonpolymeric nature of the mordant compounds of such mordanting compositions, I mean that the cationic or the basic mordant does not have regularly occurring units containing the cationic group beyond the dimer structures. However, the ballast group attached to the quaternary or ternary atom of the cation group can contain repeating groups such as tetraethoxy, polymethylene, etc.

EXAMPLE 13 A silver image transfer receiving element is made by coating a paper support in succession with (1) aqueous gelatin having dispersed in it (a) a solution of 4,4'-bis (5,7-di-t-amylbenzoxazol-Z-yl) stilbene in copoly(butyl methacrylate acrylic acid) :15 by weight prepared for coating as described in Example 1 and (b) baryta, (2) a layer of polyethylene that is treated by corona discharge (as described in US. patents, such as 3,200,842, 2,864,- 755, 2,864,756, etc.) just prior to coating with (3) a layer of aqueous gelatin containing about by weight of a dispersion of colloidal silver so that about 150 ,ug. of colloidal silver are coated per square foot.

EXAMPLE 14 A silver image transfer receiving element is made by coating a paper support in succession with (1) a layer of an aqueous gelatin baryta coating composition, (2) a layer of aqueous gelatin having dispersed in it a solution of 4,4'-bis(5,7-di-t-amylbenzoxazol) stilbene in copoly (butyl methacrylate methacrylic acid) 85:15 by weight, prepared for coating and coated as described in Example 1, and (3) a layer of aqueous gelatin containing about 10% by Weight of a dispersion of colloidal silver so that about 150 g. of colloidal silver are coated per square foot.

EXAMPLE 15 A silver image transfer receiving element is made by coating a paper support with a layer of aqueous gelatin having dispersed in it a solution of 4,4'-bis(5,7-di-t-amylbenzoxazol-Z-yl) stilbene in poly (t-butyl methacrylate) prepared for coating as described in Example 1, but also having dispersed in it colloidal silver and coating so that there is 10 mg. of the brightener, 500 mg. of poly (tbutyl methacrylate), 150 ,itg. of colloidal silver and 500 mg. of gelatin per square foot.

EXAMPLE 16 A separate piece of light image exposed photographic element comprising a film support coated with a negative speed gelatin silver bromoiodide emulsion is contacted in the dark with the colloidal silver containing layer of a piece of the image receiving element made in each of Examples 13, 14 and 15 in the presence of a conventional silver image transfer developer composition comprising water, alkali, hydroquinone, sodium thiosulfate, etc. After development is completed, the image receiving element is stripped from the processed photographic element. The highlight portions of the silver image reproductions in each of the receiving sheets are substantially brightened by my brightener. Comparisons made with similar prints made using identical image-receiving elements, excepting that the brightener is dissolved in di-nbutylphthalate instead of the polymeric solvents used in Examples 13, 14 and 15, show that my prints retain the brightener for substantially longer periods of exposure to light.

EXAMPLE 17 A dye image transfer receiving element is made like the receiving element in Example 13, excepting that the layer 3 is replaced by a layer of aqueous gelatin containing the mordant cetyl trimethyl ammonium bromide so that 150 mg. of mordant and 300 mg. of gelatin are coated per square foot.

EXAMPLE 18 A dye image transfer receiving element is made like the receiving element in Example 14, excepting that the layer 3 is replaced by a layer of aqueous gelatin containing the mordant cetyl trimethyl ammonium bromide so that 150 mg. of mordant and 300 mg. of gelatin are coated per square foot.

EXAMPLE 19 A dye transfer receiving element is made like the receiving element in Example 15, excepting that the colloidal silver is replaced by the mordant cetyl trimethyl ammonium bromide so that 150 mg. of mordant are coated per square foot.

16 EXAMPLE 20 Separate pieces of a color film described in Example 1 of Barr et al., US. Pat. 3,227,551, are exposed to an original colored image and contacted with the mordant containing layer of the receiving elements made in Example 17, 18 and 19 in the presence of a developer solution as described in Example 1 of U.S. Pat. 3,227,551. After 5 minutes development at F., the receiving elements with their color positive reproductions of the original image are stripped from the processed color film. The highlight areas of these color prints (in the receiving elements) are brightened by my brightener composition. Comparisons made with color prints pro duced exactly the same way, except that the brightening agent in the dye image-receiving elements isdissolved in di-n-butylphthalate, show that the brightener in color prints made according to my invention is substantially more stable to prolonged exposure to light than color prints outside my invention. 1 a N Brightening agents of Formula II in which G and G each represent C and X and X each represent 0, S or NR are advantageously synthesized by reacting one mole of a compound of Formula III 'with two moles of a compound of Formula IV, V, VI, or VII.

(III) 0 R4 RI R. RI R1 0 t F l t I I t |(or corresponding dtcarboxyllc acid) R! ll Rn n Ru Ru wherein R through R m and p are as defined previously and X represents 0, S or NR in which R is as defined previously, Many of the bis(benzoxazol-2-yl)stilbenes used according to my invention are described in US. Pat. 3,260,715 and in US. Pat. 3,322,680. The 4,4'-bis(benzothiazol-Z-yl stilbenes, 4,4'-bis- (naphthothiazol-Z-yl) stil benes, the 4,4-bis(benzimidazol-Z-yl)stilbenes and 4,4-

17 bis(naphthimidazol -2-yl)stilbenes are advantageously prepared by methods analogous to those shown for preparing the 4,4-bis(benzoxazol-2-yl)stilbenes.

Unsymmetrical substituted stilbenes of Formula II in which X and X are 0, S or NR are advantageously synthesized by reacting the di(acid chloride) of stilbene with an excess of phenol in alkaline solution to produce the diester. 4-carboxy-4'-phenoxycarbonyl stilbene is prepared by partial hydrolysis of the diester, then the free carboxylic acid group is transformed into the acid chloride by treatment with thionyl chloride. The acid chloride is then reacted with the appropriate compound of Formula III, IV, V, VI, or VII. The remaining phenyl ester group is then hydrolyzed, to the carboxy group, which is converted to the acid chloride and then this intermediate reacted with the appropriate compound of Formula III, IV, V, VI or VII to make the desired unsymmetrical stilbene.

Brighteners of Formula II in which X, X, G and G are N, m=p=2, are advantageously made by diazotizing 4,4'-diaminostilbene then coupling each mole of the 4,4-diazotized stilbene with two moles of o-nitroanline to make the corresponding 4,4-bis(2 nitrophenylazo)stilbene which is then reduced with zinc dust and sodium hydroxide in alcohol to produce the 4,4'-bis (benzotriazol-2-yl)stilbene. The symmetrical as Well as the unsymmetrical stilbene brighteners with benzotriazol-Z- yl groups are known in the prior art. The brightener 4-(a-naphthotriazol-2-yl) 4' octylstilbene is described generically by US. Pat. 3,406,070.

Brighteners of Formula II in which X and X are CR groups and G and G' are nitrogen atoms, m=p=2, are advantageously prepared by treating a compound of the formula R n -bH-Nn--onon R13 NO:

wherein R, R11 R12, R and R are as defined previously, with powdered zinc to produce the corresponding stilbene compound followed by treatment with tin and hydrochloric acid to produce the desired brightener compound.

The brightener 4-(5,7-di-t-amylbenzothiazol-2-yl) 4'- (4-octyloxazol-2-yl)stilbene is advantageously prepared by reacting 4amido-4-(5,7-di-t-amylbenzothiazol 2 yl) stilbene with u-bromomethyl octyl ketone, then reacting the reaction product with NH then removing water. The brightener 4-(5,7-di-t-amylbenzothiazol-Z yl) 4 (4- octylimidazol-2-yl)stilbene is advantageously prepared by reacting 4-amido-4-(5,7-di-t amylbenzothiazol 2 yl) stilbene with u-bromomethyl octylketone, reacting the reaction product with NH removing one mole of water, treating again with NH and again removing one mole of water.

The polymers used to advantage as solvents according to my invention are prepared by methods well known in the polymer art. Many of the polymers are available commercially.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. A light-sensitive photographic element comprising a support having coated thereon at least one silver halide layer and at least one hydrophilic colloid layer having dispersed therein small particles consisting of a solid solution of an oil-soluble vinylene brightening agent in a hydrophobic polymer, said polymer having a glass transi- (VIII) 18 tion temperature above about 25 C. and being selected from the group consisting of a polymer having recurring units of acrylonitrile, a polymer having recurring units of at least one alkyl alkacrylate, and a polyamide having recurring units of in which at is an integer of from 1 to 12.

2. A photographic element as claimed in claim 1, wherein said brightening agent has the formula:

wherein T represents a bivalent group selected fromthe class consisting of vinylene, a styrene group and a stilbene group; G and G each represent a member selected from the class consisting of C and N; X and X each represent a member selected from the class consisting of O, S, NR, N and OR; such that when G and G each represent C, then X and X each represent a member selected from the class consisting of O, S and NR, and such that when G and G each represent N, then X and X each represent a member selected from the class consisting of N and CR; tR represents a member selected from the class consisting of hydrogen, an alkyl group and an aryl group; M and M each represent the non-metallic atoms required to complete a heterocyclic nucleus selected from the class consisting of an oxazole, a benzoxazole, a naphthoxazole, a thiazole, a benzothiazole, a naphthothiazole, an indazole, a benzindazole, an imidazole, a benzimidazole, a naphthimidazole, a triazole, a benzotriazole and a naphthotriazole; n is an integer of from 1 to 2; and G represents a member selected from the class consisting of hy drogen, an alkyl group, and an aryl group.

3. A photographic element as claimed in claim 1, wherein said brightening agent has the formula:

S Q o c 1l group, a --NHSO Q group, a

group, a

-group, a p

- L N/ I group, a

Qz group and a V 0 Q -NHiigroup; Q and Q each represent amember selected from the class consisting of hydrogen, an alkyl group, and an aryl group; Q represents a member selected from the class consisting of an alkyl group and an aryl group; L represents a member selected from the class consisting of acyl group, an ureido group, a .SO Q group and group; R and R10 each represent a member selected from the classconsisting of hydrogen, alkyl having from 1 to I'Sfcarbou atoms and an aryl group; G and G each represent a member selected from the class consisting of Cand N; X and X each represent a member-selected from the class consisting of O, S, NR, N and CR such that when G and G each represent C, then X and X each represent a member selected from the class consisting of 0, S and NR and such that when G and 6' each rep resent N, then X and X each represent a member selected from the class consisting of N and CR; 'R represents a member selected from the class consisting of hydrogen, alkyl having from 1 to 22 carbon atoms and an aryl group; Z and Z each represent a member selected from the class consisting of hydrogen, alkyl, aryl, taken together Z and Z represent the non-metallic atoms required to complete a benzene ring and taken together Z and Z represent the non-metallic atoms required to complete a naphthylene ring; Z and Z each represent a member selected from the class consisting of hydrogen, alkyl, aryl, taken together Z and Z represent the nonmetallic atoms required'to complete a benzene ring and taken together Z and Z represent the non-metallic atoms required to complete a naphthylene ring; it represents an integer of from 1 to 2; m and p each represent integers of from.1 to 2, such that when p is 1, n is 2; and G represents a member selected from the class consisting of hydrogen, an alkyl group and an aryl group. i I

4. A photographic element as claimed in claim 1, wherein said hydrophilic colloid layer containing said brightening agent is a gelatin layer.

5. A photographic element as claimed in claim '1, wherein said particles have an average diameter of less than 0.4 micron.

6. A photographic element as claimed in claim 1, wherein said particles have an average diameter of less than 0.1 micron. j I

7. A photographic element as claimed in claim 1', wherein said hydrophobic polymer has a glass transition temperature of above about 40? C. 1

8. A photographic element as claimed in claim 1 wherein said support is paper and said hydrophilic colloid layer containing said brightening agent is a gelatin layer which also contains baryta and is coated between said support and said silver halide layer.

-9. A photographic element as claimed in claim 1 wherein said hydrophobic polymer isa homopolymer of an alkyl alkacrylate, a copolymer of two different alkyl alkacrylates, a copolymer of an alkyl alkacrylate with an alkyl acrylate, a copolymer of an alkyl alkacrylate with acrylic acid, or a copolymer of an alkyl alkacrylate with methacrylic acid.

10. A photographic element as claimed in claim 1 wherein said hydrophobic polymer is a homopolymer of t-butyl methacrylate.

11. A photographic element as claimed in claim 1 wherein said hydrophobic polymer is a copolymer of butyl methacrylate and acrylic acid.

12. A photographic element as claimed in claim 1 wherein said hydrophobic polymer is a copolymer of butyl methacrylate and methacrylic acid.

13. A photographic element as claimed in claim 5 wherein said brightening agent is a styrene brightening agent.

14. A photographic element as claimed in claim 5 wherein said brightening agent is a stilbene brightening agent.

15. A photographic element as claimed in claim 5 wherein said brightening agent is 4,4'-bis(5,7-di-t-amylbenzoxazol-2yl) stilbene.

References Cited UNITED STATES PATENTS 3,047,390 7/1962 Koerber et a1. 96-82 3,406,070 10/1968 Oetiker et al. 9682 3,558,316 1/1971 Keberle a a1. 96-82 3,513,102 5/1970 Heidke 252-30112 FOREIGN PATENTS 1,149,244 5/1963 Germany 9682 1,150,274 5/1963 Germany 96-82 RONALD H. SMITH, Primary Examiner U.S. Cl. X.|R. 96-85 Po-ww UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,7 8,85 I I Dated January 29 197A Ifivenmfls) Robert J. Tuite It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 18, claim 3, that part of the formula reading:

I n \Ot. U I n I hogid a N I n-l 2 Gnu.

j u. L N A n-l Signed and sealed this 9th day of July 1974.

(SEAL) Attest: McCOY M. GIBSON, JR. I C. MARSHALL DANN Attesting Officer I v Commissioner of Patents 

